Cryogenic storage container



Oct, 16, 1962 v 3. c. HAETTINGER ErAL 3,059,114

I v CRYOGENIC STORAGE CONTAINER Filed Oct. 22, 1959 INVENToRs GEORGE C.HAETTINGER RICHARD M.` POORMAN BY ig? Q.

A TTORNEP.

United States Patent 3,059,114 CRYGENEC STORAGE CONTAHWJR George C. Haettinger and Richard M. Poorman, indianapolis, ind., assignors to Union Carbide Corporation, a corporation of New York Filed Oct. 22, i959, Ser. No. 847,9?8 7 Claims. (Si. 25083.3)

This invention relates to an improved refrigerant storage container. More particularly, it relates to such a container having an improved refrigeration system for cooling an infra-red detection cell.

Infra-red sensing apparatus is quite useful for detecting the location of objects by the infra-red or heat waves radiating from the objects. The homing mechanism on certain air-to-air missiles, for example, is operated by means of such sensing apparatus. The infra-red detection cell is most effective when maintained at an extremely low temperature, such as the temperature of liquid nitrogen. Therefore a considerable eiort has been expended by the industry to produce apparatus which effectively cools an infra-red sensing element to about liquid nitrogen temperature and which is further capable of withstanding the rigorous operating conditions encountered in such uses as in air-to-air missiles.

Cryogenic refrigerants, such as liquid nitrogen, cool by evaporation so it is necessary to provide a suitable container having extremely eiiicient insulation and at the same time providing adequate venting if such a cooling system is to be used. In view of the expense of the liquid refrigerant and the advantages of keeping refrigerant volume and weight to a minimum, especially for missile use, refrigerant dissipation must be kept at a minimum.

Liquid refrigerant dissipation is due to two principal factors. The first is vaporization caused primarily by heat reaching the refrigerant and the second is due to sloshing of the liquid when the carrier, such as a missile, is in motion. This sloshing causes the refrigerant to spill out of the iilling and vent openings provided in currently available equipment. The sloshing problem is especially critical in a horizontal cylindrical container.

Frei/ions refrigeration units for infra-red cells were crude devices using a combination fill and vent opening in the top of the container. The venting took place through an opening in the stopper placed in the fill line. This apparatus undesirably allowed liquid to ilow out of the container under sloshing conditions.

lt is accordingly an object of the present invention to provide a container for cryogenic liquids having improved insulating, lling and venting means.

it is a further object to provide such a container having substantially increased operating eciencies.

lt is still a further object to provide an infra-red detection cell with such an improved cryogenic liquid container therefor.

Other objects and advantages will be apparent from the specification and the drawing which shows a crosssection of a refrigerated container according to the present invention with an infra-red detection cell mounted therein.

The objects of the invention are accomplished in general by apparatus which comprises a double walled container having an outer wall and an inner wall space therefrom, the space between the inner and outer walls being sealed, evacuated and preferably lled with opacified insulation material. A iiller tube is provided extending through the evacuated space of the container to the inner wall of the container. A venting tube is provided which enters the container at a point adjacent to the filler tube and above the normal refrigerant level and extending across the container above and substantially lliid Patented @et l5, 1962 parallel to the refrigerant surface terminating at a point on the opposite side of the container from the point where it enters. The inner vessel is supported within the outer vessel at one end by means of a cylindrical beam member and at the other end by the lling and vent lines. In order to provide maximum support for the inner vessel, it is preferred that the filling line enter the inner vessel at a point substantially 'centrally located on one end of the vessel while the beam member be substantially centrally located on the opposite end. Such configuration is shown in the FlGURE. An infra-red detecting cell is preferably located in heat exchange relationship with the liquid refrigerant through suitable conduit means. Said conduit means also provides a mount for the infrared detection cell.

The invention will be described in more detail with rrespect to the accompanying ligure wherein the container l0 is formed from an inner vessel 14 and an outer vessel l2, both preferably constructed of aluminum or aluminum alloys. The space between the vessels is under a vacuum pressure and preferably contains an opacifled insulating jacket 16 and gas adsorbent material 18 conimunicating with the evacuated space to maintain the space under a vacuum.

ri'he term vacuum as used herein is intended to apply to sub-atmospheric pressure conditions not substantially greater than microns, and preferably below 10 microns absolute. rIhe term opaciiied insulation as used herein refers to a two-component insulating system comprising a low heat conductive, radiation-permeable material, such as silica powder or ber glass, and a radiant heat impervious material, such as aluminum or copper powder or foil, which is capable of reducing the passage of infra-red radiation rays without significantly increasing the thermal conductivity of the insulating system.

A combination of straight vacuum with polished wall surfaces could alternatively be used but is not as eifective as the above vacuum-opacied insulation system.

Adsorbent l, either in powder or pellet form, is preferably used in the insulation jacket to remove by adsorption any gas which may leak into the jacket space. This is important since no provision is made in these relatively small storage containers for re-evacuation of the insulating jacket. ln particular, zeolitic molecular sieves having pores of at least about 5 angstrom units in size, are preferred as the adsorbent since they have extremely high adsorptive capacity at the temperature and pressure conditions existing in the insulating jacket and are chemically inert toward any gases which might leak into the insulating jacket. Such use is described in U.S. Patent No. 2,900,800. However, other adsorbents such as silica gel, activated allumina and activated charcoal may also be used if so desired. Alternatively, active metal getters that function by chemically combining with inleaking and residual air may be used.

An extension 20 conveniently located at the lower portion of container l0 is used to mount infra-red detection cell Z2. in proper position with respect to the container and also to provide refrigeration to the cell. Liquid refrigerant can iiow down into extension 24 of inner vessel il or preferably a solid material 26 such as sapphire, having a high thermal conductivity and low coeliicient of thermal expansion can be used to cool the detection cell. Use of this solid :material is preferred since it simplifies fabrication and also reduces the noise level in the detection circuit created by boiling of the low temperature refrigerant near the detection cell. A sapphire window 40 is positioned in the wall of the extension 20 in front of the cell to increase infra-red transmission to the cell. When yan opacied insulation is used in the evacuated portion of extension 20, it terminates at a point above the detection cell in order to pre- 3 vent blocking the Window 40. When a solid heat conductive material is used to conduct heat from the cell to the refrigerant, the extension need not be on the lower portion of the container lbut could also be on the side since Igravity flow of refrigerant will not then be required.

Liquid refrigerant is introduced into the side of the inner vessel 14 through filling line 28 and trap Y44 which is also insulated by the opaciiied insulating jacket 16. Once the container is filled with the desired amount of refrigerant, the filling line is closed by means of a stopper (not shown) placed into filling inlet 30. Trap '44 prevents liquid from rising in line 28 when the line enters below the normal refrigerant level. During filling and subsequent storage of the refrigerant, vapors from the low-boiling point liquid refrigerant are vented through line 32. This vent line also enters from the side of the container nearV its top and extends along substantially the entire length of the inner vessel 14. Normally only vapors pass into the vent line. Under sloshing conditions, however, liquid might ow into the vent line. The relatively long distance between the inlet end 34 of the vent line and the outlet 36 requires a definite period of time before the liquid could flow out of the vent line. During this period the sloshing could subside or the container could again become in level position and liquid will either ow back into the inner vessel or be vaporized in the vent line. If the vent line were relatively short as is the filling line, under moderate sloshing conditions liquid could undesirably flow out of the vent line and present a hazard to personnel in the area as well as cause a waste of liquid. The filling and vent line are preferably constructed of tubing having low thermal conductivity, such as stainless steel. The joints between the stainless steel tubes and the aluminum vessels are formed by suitable means as brazing.

The vent line 32 is made to have a long heat transfer area within the gas space above the liquid 8. The gas Iis normally at a nonequilibrium higher temperature than the liquid. Therefore any small amount of liquid splashed into the vent Kline 32 will be subject to the higher temperature of the gas space and will evaporate so as to return its latent heat of evaporation to the gas space and insure that no liquid blows out of the vent 36. This effect can be increased by having an orifice at 34 of smaller cross section than the vent 36 so that the pressure in container 14 is at a slightly higher value than the pressure in the vent line 32. The vent line can also terminate in yan upward position to further prevent liquid from flowing into the line.

The inner vessel 14 is preferably supported Within the outer vessel 12 by means of a :beam member 3S at one end and by means of the llin-g and vent lines at the other end. The beam member is preferably constructed from low thermal conductivity plastics and is hollow to reduce cross sectional area and thus reduce heat conduction through the member. Useful materials are laminated phenolic plastics (eg. phenol-formaldehyde), melamine resins (c g. melamine formaldehyde) and trifluorochloroethylene, all of these materials being preferably reinforced with glass fiber for other suitable highstrength filler material. The beam member is conveniently and preferably xedly attached to the outer vessel and slidably and telescopically engages depression 42 in the end of inner vessel 14. This beam member prevents lateral movement of inner vessel 14 with respect to outer vessel l2.

This novel apparatus can be supplied in two general forms. The first andy .preferable form is that shown in the figure which is called -a l-piece refrigeration unit. An alternate form is a Z-piece -unit wherein the extension 20 is not included, but an opening is provided in the lower portion of the container for insertion of a properly designed extension unit.

A model having the configuration shown in the gure and containing about 0.7 liter (1.5 lbs.) of liquid nitrogen satisfactorily met operating specifications of cooling an infra-red cell for 30-34 hours without refilling.

As is evident from the above'description a number of changes and substitutions may be'made in the apparatus of the instant invention Without departing from the spirit and scope thereof.

What is claimed is:

l. A refrigeration storage apparatus for cryogenic liquids which comprises a double walled container for a liquid refrigerant, wherein the inner wall is spaced from the outer wall, said space being sealed and evacuated, a filler tube extending from the outer wall through the evacuated space to the inner wall of the container, a vent tube entering the container at a point slightly above the refrigerant liquid surface, extending above and substantially parallel to the refrigerant liquid surface and terminating at a point adjacent the opposite side of the container from the point where it entered the container.

2. An apparatus as set forth in claim l wherein the evacuated space contains an opacified insulating medium.

3. An apparatus as set forth in claim 2 wherein the filler and vent tubes pass through the container walls at adjacent points and the space between the walls in this area is greater to provide increased insulation.

4. An apparatus as set forth in claim 1 wherein the inner liquid refrigerant container formed by the inner wall is supported within the outer container formed by the outer wall at one end by the iiller and vent tubes passing therethrough and at the other end by a hollow cylindrical beam ,member characterized` by poor heat conduction rigidly connected to the outer container at one end and engaging a depression within the inner container Y -atthe other end, said insulating space further being characterized by having a gas adsorbent material therein for scavenging residual gases left after evacuation.

5. A refrigerated infra-red detection cell apparatus which comprises a double wall container for liquid cryogenic refrigerant, an inner wall defining an inner chamber and an outer wall defining an outer chamber, said inner chamber being spaced from said outer chamber, said space being filled with an opacified insulating medium and being highly evacuated, said space further containing a gas adsorbent material for scavenging gas left in the space after evacuation, a ller tube extending down from the top of the outer container within the evacuated space and entering the inner container at a point below the normal surface level of the liquid refrigerant, a trap in said filler line to prevent liquid refrigerant from rising in said filler line, a vent tube entering the double walled container at a point near the filler tube and extending across the inner container slightly above and substantially parallel to the liquid refrigerant surface and terminating adjacent the opposite'side of the inner container from that where it entered, said vent and filler tubes serving to support the inner container within the outer container at one side thereof and a hollow cylindrical beam member iixedly secured to the outer container at one end and engaging a depression in the inner container serving to support the inner container at the other side thereof, a-,double walled tube depending from the bottom of said container having an inner and outer tube connected to the inner and outer containers respectively such that the inner tube is filled with liquid refrigerant, the space between said inner and outer tubes being evacuated, an infra-red detection cell located at and in thermal contact with the lower extremity of the inner tube and a window of a highly infra-red transparent material in the outer tube opposite the infra-red detection cell.

V6. An apparatus as set forth in claim 5 lwherein the lower end of the inner depending tube is closed by a sapphire element and the infra-red detection cell is directly attached thereto and wherein the infra-red transparent window is made of sapphire.

7. A cryogenic apparatus which comprises a double wall container for liquid refrigerant, an inner Wall defining an inner chamber and an outer Wall defining an outer chamber, said inner chamber being spaced from said outer chamber, said space being lled With an opacied insulating medium and being highly evacuated, said space further containing a gas adsorbent material yfor scavenging gas left in the space after evacuation, a filler tube extending down from the top of the outer container Within the evacuated space and entering the inner container at a point below the normal surface level of the liquid refrigerant, a trap in said ller line to prevent liquid refrigerant from rising in said iller line, a vent tube entering the double Walled container at a point near the ller tube and extending across the inner container slightly above and substantially parallel to the liquid refrigerant surface and terminating adjacent the opposite side of the inner container from that where it entered, said vent and ller tubes serving to support the inner container Within the outer container at one side thereof and a hollow cylindrical beam member xedly secured to the outer container at one end and engaging a depression in the inner container serving to support the inner container at the other side thereof, a double Walled tube depending from the bottom of said container having an inner and outer tube connected to the inner and outer containers respectively such that the inner tube is lled with liquid refrigerant, the space between said inner and outer tubes being evacuated, a device to be refrigerated located at and in thermal contact with the lower extremity of the inner tube.

References Cited in the ile of this patent UNITED STATES PATENTS 2,547,173 Rittner Apr. 3, 1951 2,671,154 Burstein Mar. 2, 1954 2,777,295 Bliss et al. Jan. 15, 1957 2,834,187 Loveday May 13, 1958 2,968,161 Bliss Jan. 17, 1961 

